A magnetic disk drive, which serves as a disk apparatus, includes a casing having a base and a top cover, and an actuator supporting a rotatable magnetic disk, a magnetic head, and the like, are disposed within this casing. The base is formed from a metallic material such as aluminum, and a black electro-paint, for example, is applied onto inner and outer surfaces of the base.
In assembling such a magnetic disk drive, when the top cover is attached to the base, corner portions of the top cover contact the inner surface of the base. Consequently, the inner surface of the base is often scratched (and wear tracks are left) or the electro-paint peels off and such peeling is often recognized as scratches. When the base and the top cover each include a plurality of corner portions, the occurrence of the above scratches tends to be concentrated near the corner portions of the base. When the scratches or the peeling of the electro-paint occurs, the base is often determined as a manufacturing failure. As a result, there is a risk of reduced manufacturing yield and increased of manufacturing cost.